Good visibility through the windows of a vehicle is critical for safe driving. On winter days, the windows of the vehicles often have a thin layer of frost. The frost on the windows could badly affect the driver's visibility. Therefore, it is necessary to scrape the frost off the windows of the vehicle before driving.
To get rid of the frost on the windows or lamp of the vehicles, a resistance wire is coated on the windows or lamp to form a conductive layer. A voltage is applied to the conductive layer to generate heat and melt the frost. The conventional resistance wire is made of metal or alloy. However, when a diameter of the resistance wire is 1 micrometer −50 micrometers, a tensile strength of the resistance wire will be significantly reduced.
Since carbon nanotubes have good mechanical properties, carbon nanotubes are used to form the resistance wire. A conventional carbon nanotube wire comprises a plurality of microscopic carbon nanotubes connected with each other. Although the carbon nanotube wire has high mechanical strength, the connection between adjacent carbon nanotubes has high resistance, and the overall conductivity of the carbon nanotube wire is not good. Therefore, when the carbon nanotube wire is used to get rid of the frost on the windows or lamp of the vehicles, because a voltage of a vehicle power supply is smaller, usually 12 v, it is difficult to meet the heating requirements.
In order to improve the conductivity of the carbon nanotube wire, the surface of the carbon nanotube wire may be coated by a metal layer with a thickness of 1 nanometer to 50 nanometers. The electric conductivity of such a coated carbon nanotube wire is improved. However, the metal layer is thin, and is easily oxidized, so the durability of the coated carbon nanotube wire is low.